Telophase is the fifth phase of mitosis and the final phase of meiosis as well.
In meiosis, there are two phases: telophase I and telophase II.
This phase involves the separation stage of duplicate genetic materials carried in the cell nucleus of the parent cells.
These genetic materials end up forming two identical daughter cells.
Telophase starts after replication when the paired chromosomes are separated and pulled to the cell’s opposite poles.
What happens during Telophase?
During telophase, a nuclear membrane forms around each set of chromosomes.
This process separates the nuclear DNA from the cytoplasm.
The chromosomes then start to uncoil, becoming diffuse and less compact.
This phase is followed by cytokinesis, which divides the cytoplasm of the parental cell into two daughter cells.
Telophase in Mitosis
Telophase in mitosis is significantly an extension of anaphase and metaphase that is controlled by the dephosphorylation of the mitotic cyclin-dependent kinase (CDK) substrate.
Various mechanisms take place within this phase, leading to the formation of new daughter cells. These include:
Dephosphorylation of the mitotic Cyclin-Dependent Kinase substrate (Cdk)
Phosphorylation of the mitotic Cyclin-Dependent Kinase (CDK) substrate leads to spindle assembly, chromosome condensation, and nuclear envelope breakdown, which occur during the initial stages of mitosis.
Dephosphorylation of the mitotic CDK substrate occurs as the mitotic cell cycle comes to an end in telophase.
This dephosphorylation enables spindle disassembly, nuclear envelope reformation, and chromosomal decondensation in the new daughter cells.
One of the most significant CDKs is Cdc14, which is initially activated by being released into the nucleus from the nucleolus and then exported to the cytoplasm.
Cdc14’s initial function occurs during early anaphase, where it stabilizes the mitotic spindles and promotes the release of more Cdc14 into the nucleus, where it becomes restricted.
This nuclear restriction becomes important in the Mitotic Exit Network (MEN), where Cdc14 plays a major role in triggering spindle disassembly and nuclear envelope reassembly during telophase.
Cdc14 also mediates dephosphorylation by activating downstream regulatory proteins specific to telophase, such as CHD1 dephosphorylation proteins.
These proteins target proteolysis, resulting in cellular switching activity that eventually transitions the cell into the G1 phase of interphase.
Dephosphorylation also causes the distancing of chromosomes from the metaphase plate, which triggers early telophase.
Cdc48 further activates telophase mechanisms—including spindle disassembly, nuclear envelope assembly, and chromosome decondensation—through ubiquitination in the proteasomes.
Mitotic spindle disassembly
This process involves the shortening of the kinetochore microtubules.
It pulls the chromosomes toward the poles of the cell.
It results in the separation of the chromosomes from each other.
Nuclear envelop reassembly
It results in the separation of the chromosomes from each other.
Nuclear envelope reassembly involves the reconstruction of the double nuclear membrane, the formation of nuclear pore complexes, and the formation of the internal nuclear lamina into the inner nuclear membrane.
These nuclear structures are dismantled during the prophase and metaphase phases.
During metaphase, the nuclear membrane is absorbed by the endoplasmic membrane.
In telophase, nuclear membrane protein-containing vesicles from the endoplasmic reticulum are targeted to the chromatins.
This targeting facilitates the formation of the nuclear envelope and the reestablishment of the double-layered nuclear membrane.
Chromosome condensation
Chromosome condensation (decompaction) leads to the formation of expanded chromatin.
The compact chromosomes are essential for the cell’s preparation and initiation of interphase.
Condensation occurs in parallel with nuclear envelope assembly.
This process is mediated by the Mitotic Exit Network (MEN) through Cyclin-Dependent Kinase (CDK) dephosphorylation.
CDK dephosphorylation plays a key role in restarting the interphase.
Telophase in mitosis: Summary
Telophase is the final phase of mitosis.
The processes involved are a reverse of what occurred in anaphase and metaphase.
A new nuclear membrane is formed around each set of chromosomes.
The chromosomes unfold back into chromatins.
The nucleoli reappear within each nucleus.
The cell starts to enlarge again.
During this phase, the sister chromatids reach the opposite poles of the cell.
Small nuclear vesicles begin to reform around the chromosomes at each end of the cell.
The nuclear envelope reforms by associating with the chromosomes, forming two nuclei within the newly forming cell.
The kinetochore microtubules are dissolved during this phase.
The polar microtubules continue to elongate.
As the nuclear envelope is reformed, the chromosomes begin to condense and become more diffuse.
Telophase in Meiosis
Telophase I
Telophase I occurs after homologous chromosomes have been separated.
During this phase, the homologous chromosomes separate into distinct nuclei.
The cell reforms its nuclear envelope around each set of chromosomes.
Spindle fiber microtubules are disassembled.
The cell proceeds to cytokinesis, dividing the cytoplasm into two daughter cells.
The cell then enters a resting phase known as interkinesis before proceeding to meiosis II.
Telophase II
Telophase II occurs after the sister chromatids of each chromosome have already separated.
During this phase, the sister chromatids are surrounded by a new nuclear membrane, forming distinct nuclei.
Although the cells originate from the same chromosome, differentiation occurs during recombination in prophase I, where parts of the homologous chromosomes were exchanged.
By the end of meiosis, four cells are formed, each containing two alleles for each gene.
These alleles are separated in various ways, combining with alleles from other genes to increase genetic diversity.
Reference
A study on the kinesin-mediated mechanism coupling centrosomes to nuclei (ResearchGate): https://www.researchgate.net/publication/233538316_A_kinesin-mediated_mechanism_that_couples_centrosomes_to_nuclei
Article on telophase and cell division processes (NCBI): https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3501164/
Detailed information about cell processes, including telophase (Cell): https://www.cell.com/cgi/content/full/117/3/361/DC1
Flashcards on the cell cycle and mitosis (Quizlet): https://quizlet.com/118059230/the-cell-cycle-and-mitosis-flash-cards/
Overview of the stages of the cell cycle and mitosis (Owlcation): https://owlcation.com/stem/Stages-of-the-Cell-Cycle-Mitosis-Part-2-of-2
Wikipedia page on telophase: https://en.m.wikipedia.org/wiki/Telophase
Biology Dictionary entry for telophase: https://biologydictionary.net/telophase/
Biology Dictionary entry for prophase: https://biologydictionary.net/prophase/
A Yahoo Answers discussion on cell division: https://answers.yahoo.com/question/index?qid=20070515070459AATdqtH
Definition of daughter cells (ThoughtCo): https://www.thoughtco.com/daughter-cells-defined-4024745
SparkNotes overview of mitosis: https://www.sparknotes.com/biology/cellreproduction/mitosis/section3/
ScienceDirect article on telophase and related biological processes: https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/telophase
ResearchGate publication on Cdc14's role in DNA replication and cell division: https://www.researchgate.net/publication/6680673_Novel_Role_for_Cdc14_Sequestration_Cdc14_Dephosphorylates_Factors_That_Promote_DNA_Replication
NCBI article on the role of Cdc14 in cell cycle progression: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2043359/
Explanation of what separates DNA from the cytoplasm in eukaryotic cells (Answers.com): https://www.answers.com/Q/What_separates_DNA_from_the_cytoplasm_in_eukaryotic_cells
Answers.com query on the number of cells formed at the end of meiosis II: https://www.answers.com/Q/How_many_cells_have_formed_at_the_end_of_meiosis_2
